Floor price (also called bid floor or minimum CPM) is the minimum price a publisher will accept for a programmatic ad impression. When an SSP routes an impression to ad exchanges, it includes the floor price in the bid request. DSPs that bid below the floor are excluded from the auction. If no DSP bids above the floor, the impression goes unfilled — or falls through to backup demand sources (lower-priority networks, direct-sold campaigns, house ads).
The floor-price trade-off
Higher floors → higher average eCPM per filled impression (low-quality demand excluded) BUT lower fill rate (more impressions go unfilled, capturing zero revenue). Lower floors → higher fill rate (almost everything fills) BUT lower average eCPM (cheap demand wins more often). Publishers tune floors to maximize total revenue: filled-impression count × average eCPM.
Tuning best practice: test floors in 10-15% increments. Watch the impact on (a) fill rate, (b) average eCPM, (c) total revenue (the product). Most publishers find a sweet spot where modest floor increases pay back via eCPM lift without crashing fill rate. Too-low floors leave money on the table; too-high floors lose more revenue from unfilled impressions than they recover from eCPM lift.
Floor types: most modern SSPs support per-impression floors (varies by user segment, time of day, geo) rather than fixed global floors. A US iOS user on a weekday morning may have a $5 floor; an emerging-market Android user on a Sunday night may have a $0.50 floor. Sophisticated yield management runs hundreds of dynamic floor segments simultaneously.
Floor price: the fill-rate vs eCPM trade-off
| Floor level | Fill rate | Avg eCPM | Risk |
|---|---|---|---|
| Too low | Very high | Low | Leaves money on the table |
| Tuned (sweet spot) | High | Strong | Maximizes total revenue |
| Too high | Low | Highest per fill | Unfilled losses exceed eCPM gains |
Total revenue = filled impressions × average eCPM. Tune in 10-15% increments and optimize the product of both — never fill rate or eCPM in isolation.